to convey the far-reaching nature of Rabbi Yosei’s statement, as he is lenient in a case of uncertainty whether the eiruv was burnt the previous day or only after nightfall, even though the eiruv is now entirely destroyed. Additionally, the mishna taught the case of teruma that became ritually impure to convey the far-reaching nature of Rabbi Meir’s statement, as he is stringent even though the teruma itself is still present, and there is only an uncertainty about when it became impure.

The Gemara questions the mishna’s ruling itself: Does Rabbi Meir really hold that in cases of doubt one must be stringent? Didn’t we learn the following in a mishna: If a ritually impure person descended to immerse in a ritual bath, and there is doubt whether he actually immersed or he did not immerse; and even if he certainly immersed, there is doubt whether he immersed in a ritual bath containing forty se’a of water, the minimal amount of water necessary for the ritual bath to be valid, or he did not immerse in forty se’a; and similarly, if there are two adjacent ritual baths, one of which has forty se’a of water in it and is therefore valid, and one of which does not have forty se’a of water in it, and he immersed in one of them, but he does not know in which of them he immersed; in each of these cases, owing to one’s doubt, he remains ritually impure?

במה דברים אמורים בטומאה חמורה

In what case is this statement, which maintains that in cases of doubt one is considered impure, said? It is said with regard to severe forms of ritual impurity, i.e., those imparted by a primary source of ritual impurity.

However, with regard to lenient forms of ritual impurity imposed only by rabbinic decree, such as one who ate half a half-loaf of impure foods; and similarly, one who drank impure liquids; and one whose head and most of his body came under drawn water, as opposed to spring water or rainwater, in which case the Sages decreed that person to be ritually impure; or if three log of drawn water fell on one’s head and most of his body, in which case the Sages also decreed that person to be impure; and if in any of these cases one descended to immerse himself in a ritual bath to purify himself of the rabbinically decreed impurity, and there is doubt whether he actually immersed or he did not immerse; and even if he certainly immersed, there is doubt whether he immersed in forty se’a of water or he did not immerse in forty se’a; and similarly, if there were two ritual baths, one of which has forty se’a of water in it and one of which does not have forty se’a of water in it, and he immersed in one of them, but he does not know in which of them he immersed; in all of these cases, owing to his doubt, he is ritually pure.

רבי יוסי מטמא

Rabbi Yosei disagrees and renders him ritually impure. In any event, it is clear that, according to the unattributed mishna, which is generally presumed to reflect the opinion of Rabbi Meir, the halakha is lenient in cases of doubt relating to ritual impurity that is due to rabbinic decree. Why, then, doesn’t Rabbi Meir agree that we should be lenient in cases of doubt relating to an eiruv, which is also of rabbinic origin?

קסבר רבי מאיר תחומין דאורייתא נינהו

The Gemara answers: Rabbi Meir holds that the prohibitions relating to Shabbat limits are prohibited by Torah law, and therefore the uncertainties in the mishna involve a Torah prohibition, with regard to which one may not be lenient.

The Gemara asks: Does Rabbi Meir really hold that the prohibitions of Shabbat limits are prohibited by Torah law? Didn’t we learn in a mishna: When taking measurements related to Shabbat boundaries, if a fifty-cubit rope is held at either end by two people, the distance between them is deemed to be fifty cubits, even if the distance on the ground is greater, owing to inclines and depressions? If there is a hill or incline between them that cannot be swallowed by the fifty-cubit measuring rope, so that the usual mode of measurement cannot be used, in this situation, Rabbi Dostai said in the name of Rabbi Meir: I heard that we pierce mountains, i.e., we measure the distance as if there were a hole from one side of the hill to the other, so that in effect we measure only the horizontal distance and ignore the differences in elevation.

And if it should enter your mind to say that the prohibitions relating to Shabbat limits are prohibited by Torah law, would it be permitted to pierce the mountains? Didn’t Rav Naḥman say that Rabba bar Avuh said: We may not pierce mountains when measuring the boundaries of cities of refuge nor when measuring which city is closest to a corpse and is therefore obligated to perform the rite of the heifer whose neck is broken, because those laws are from the Torah; therefore, a more stringent policy is used to measure the distances precisely?

The Gemara answers: This is not difficult, as there is no contradiction between the two statements. This statement, according to which Shabbat limits are by Torah law, is his; that statement, in which he is lenient, is his teacher’s. The language of the mishna is also precise according to this explanation, as we learned: In this case, Rabbi Dostai bar Yannai said in the name of Rabbi Meir: I have heard that we pierce mountains. This formulation indicates that Rabbi Meir did not state his own opinion. Rather, he transmitted a ruling that he had heard from his teacher, even though he did not agree with it himself. The Gemara concludes: Indeed, conclude from this that this resolution is correct.

ורמי דאורייתא אדאורייתא לרבי מאיר

The Gemara continues: There is still room to raise a contradiction between one ruling with regard to Torah law and another ruling with regard to Torah law, according to the opinion of Rabbi Meir.

As we learned in a mishna: If one touched one other person at night, and he does not know whether the person he touched was alive or dead, and the following day he arose and found him dead, and he is in doubt as to whether or not he contracted ritual impurity as a result of having come into contact with a corpse, Rabbi Meir renders him ritually pure. It is assumed that the deceased was still alive until the point that it is known with certainty that he is dead. And the Rabbis render him ritually impure because it is assumed that all ritually impure items had already been in the same state as they were at the time they were discovered. Just as the deceased was found dead in the morning, so too, it may be presumed that he was dead when he was touched in the middle of the night. Therefore, Rabbi Meir is lenient even with respect to an uncertainty relating to a Torah law, and he holds that a person is presumed to be alive until it is known with certainty that he died. Why, then, is he stringent concerning doubt as to whether the eiruv had already become impure on the previous day or only after nightfall? Here too, one should assume that the eiruv is ritually pure until he knows with certainty that it became defiled, and so the eiruv should be valid, even if Shabbat limits are considered Torah law.

The Gemara answers: Rabbi Yirmeya said: The mishna is referring to a case where a creeping animal that imparts ritual impurity was on the teruma that was used to establish the eiruvfor the entire twilight period. The Gemara asks: If so, in that case, would Rabbi Yosei say that an eiruv whose validity is in doubt is valid? There is no uncertainty in this case.

It was Rabba and Rav Yosef who both said: The doubt here does not result from the facts of the case themselves, but from conflicting testimonies and an inability to decide between them. Here, we are dealing with two sets of witnesses, one of which says: The terumabecame impure while it was still day, before the onset of Shabbat; and one of which says: The teruma became impure only after nightfall.